This invention relates to magnets, and in particular to a magnet assembly that provides a variable magnetic field, and to a method of navigating medical devices using such a magnet assembly.
Permanent magnets are capable of providing strong magnetic fields useful in many applications. In some applications, such as in magnetic surgery, it is desirable from time to time to change the direction of the magnetic field. In the past this could only be accomplished by some combination of translations and rotations of the magnets. In the case of magnetic surgery, this means that a relatively large exclusion zone must be maintained around a patient. This exclusion zone interferes with the placement of other medical equipment, including imaging equipment necessary to monitor the magnetic surgery, and with access to the patient.
The assembly of the present invention comprises at least two rotatably mounted magnets having magnetization directions such that rotation of at least one of the magnets changes the direction of the magnetic field at an application point in the patient. Thus by a simple rotation of the magnets within the assembly the direction of the applied magnetic field can be changed, and the combination of rotating the magnets and rotating the magnet assembly allows a magnet field in virtually any direction, eliminating the need for large exclusion zones around the patient to accommodate translation of the magnet needed with prior art magnets.